With continuous improvement of mobile phone production technology particularly after the appearance of smart mobile phones, there are dramatically more functions in mobile phones, and video and camera functions of mobile phones have almost become essential functions of every mobile phone. With the increasing popularization of high pixel cameras (e.g., 5M, 8M, and 12M cameras) in smart mobile phones, the photographic quality of mobile phones is getting more close to that of consumer digital cameras. However, a high pixel mobile phone camera in the prior art generally does not include some optical and mechanical components of a digital camera. Such an absence of hardware will obviously make the photographic effect of a camera mobile phone be much worse than that of a digital camera. A current camera mobile phone usually includes at most one autofocus motor for realizing the function of changing to different focuses, and the control applied to a lens by the autofocus motor is at most to make the lens to approach or leave an image sensor in a single dimension. In an advanced digital camera, a lens is simultaneously controlled to move in multiple dimensions relative to an image sensor by more complicated mechanical devices, for example, the lens is moved horizontally to realize optical image stabilization (OIS), or the lens is tilted moderately to realize lens tilt photography.
In order to make that the photographic effect of camera mobile phones further approach that of digital cameras, many international famous mobile phone autofocus motor manufacturers have started to develop three-axis autofocus motors, for example, TDK, Mistumi, and Foxconn have already manufactured optical image stabilization autofocus motors based on horizontal movements of lenses. However, these motors have very complicated structures, large sizes, and high power consumption, and therefore they have never been popularized in the market of smart mobile phones.
To this end, AP PHOTONICS LIMITED has also developed an autofocus motor capable of controlling lens movement in 3-dimension, which consists of lens tilt in 2-dimension and a linear motion along the optical axis and realizes optical image stabilization and autofocus functions. This makes a breakthrough in miniaturization of components. The size of a three-axis motor is manufactured to be as small as that of a conventional single-axis motor for the first time, the power consumption is controlled effectively, and thus the use of three-axis motors in mobile phones is really feasible. This motor design provided by AP PHOTONICS LIMITED uses several (three or more) identical actuators distributed around an lens to drive the lens to move independently in a direction that is substantially parallel to an optical axis, and realizes focusing and a controllable tilt angle of the lens by controlling the movement amount of each actuator; when the lens is tilted, an equivalent horizontal movement of the lens is simultaneously generated, so that an optical image stabilization photographic effect can be realized by associating this design with a gyroscope sensing control. However, this motor has some defects that cause difficulty in mass production and it is difficult to be matched with motor driving circuits, therefore, it is not widely popularized in smart mobile phones, either.
A current autofocus motor provided by AP PHOTONICS LIMITED usually adopts four identical actuators to jointly drive a lens to move, wherein each of the actuators makes a contribution to focusing and tilting of the lens, and therefore the four actuators need to coordinate and cooperate so that the posture of the lens can be accurately controlled. When the lens moves, three controlling parameters, which are the motor focusing position, the X-tilting angle, and the Y-tilting angle, need to be converted into four current parameters for driving the four actuators, so that the required control can be realized. Accordingly, complicated conversion algorithm needs to be embedded into a control chip of the motor. In this autofocus motor, the impedance of a coil of each actuator is relatively small (less than 10Ω), and is inconvenient to match with a conventional driving circuit; and the four actuators, which are independent of each other, need to be controlled by four identical driving circuits. Each of the driving circuits undertakes a task of controlling the focusing position and the tilting angle of the motor, and the driving current thereof is the superposition of the current controlling focusing and the current controlling tilting. Due to the restriction to the current output dynamic range of each driving circuit, the change of the focusing current will affect the dynamic range of the tilting current, and therefore the focusing movement and the tilting movement are prone to interfere with each other.